My background is chemistry rather than physiology, which may explain where I am stuck.
This has the shape of a fact but I cannot find its origin.
What I found instead were three secondary sources all citing each other.
Is there data behind this, or is it received wisdom?
Read SURMOUNT-5 by arm, because the arm is the unit of randomisation and every figure worth quoting is defined at that level. A programme that randomised several dose levels reports each one separately, with its own sample size and its own interval, and the pooled number that circulates afterwards describes a group nobody was assigned to. Take the primary publication and its supplementary tables rather than a summary of them: one is organised by arm, the other by whichever figure was largest. And check the estimand — what happened to everyone assigned, or what happens to those who kept taking it — because the two answer different questions and are routinely quoted as though they were one.
The half-life is around five days, so steady state arrives after about four weeks and titration is monthly for that reason.
SURPASS-2 compared tirzepatide against semaglutide 1 mg in type 2 diabetes and reported greater HbA1c and weight reductions across the tirzepatide doses. It did not compare against semaglutide 2.4 mg, and the distinction matters when the trial is quoted.
| Δ mass (Da) | Most likely cause | Distinguishing feature |
|---|---|---|
| +1 | Deamidation (Asn or Gln) | New peak, slightly earlier retention |
| −17 | Loss of ammonia | Often with deamidation |
| −18 | Dehydration / succinimide | pH-dependent, reversible |
| +16 | Oxidation (Met, Trp) | Earlier retention, light-related |
| −128 | Missing Gln or Lys | Deletion sequence from synthesis |
| 0 | Isomer: racemisation or scrambling | Same mass, shifted retention |
Gastrointestinal adverse events are dose-related and mostly occur during escalation, with rates broadly comparable to single-agonist comparators at clinically comparable exposures.
The imbalanced receptor pharmacology is reported in the primary pharmacology publications and is not a secondary inference.
Nothing here is medical advice.
Five-day half-life, four-week steady state, four-week titration steps.
HPLC purity, identity confirmation and quantified content on the vial you actually hold. Reports arrive with the chromatogram attached, not just a number.
Submit a sampleFounded 1998. ISO 9001 and cGMP certified, 1,500+ staff and 200+ patents. The synthesis house behind a great many of the vials that get sent out for testing - batch-specific documentation with every order.
Visit GL BiochemThe relevant design point is that receptor potency is greater at GIP than at GLP-1, which is deliberate and is the "imbalanced" part of the description.
Receptor pharmacology is imbalanced: potency at the GIP receptor approaches that of native GIP, while potency at the GLP-1 receptor is lower relative to native GLP-1. That asymmetry is a design choice and its consequences are still being worked out.
SURMOUNT-OSA used polysomnography rather than symptom scales, which is why its apnoea–hypopnoea index result is quotable in a way that questionnaire-based results are not.
Research-use material is not approved for human use.
Quote the comparator dose whenever you quote SURPASS-2.
This is the agent where the head-to-head evidence against another agent in the class actually exists, which makes comparison arguments unusually tractable.
For research-grade material the practical issues are identity confirmation and quantified content; a 39-residue peptide with two non-standard features is not something a purity figure alone characterises.
Specifically, the peptide is based on the GIP sequence rather than the GLP-1 sequence, with modifications conferring GLP-1 receptor activity, DPP-4 resistance and a C20 fatty diacid at position 20 for albumin binding.
Peptide mapping rather than intact mass is the appropriate identity test for this molecule, because several plausible substitutions are mass-neutral.
SURPASS for glycaemia, SURMOUNT for weight, SURMOUNT-OSA for apnoea. Do not mix them.
The honest answer is that on the endpoints measured it outperforms single-receptor agonism, and the mechanism for the margin is still debated.
The elimination half-life is approximately five days, giving steady state at about four weeks and making a four-weekly titration interval the pharmacologically coherent one.
SURMOUNT-1 through SURMOUNT-4 cover obesity indications including maintenance after withdrawal, and SURMOUNT-OSA covers obstructive sleep apnoea.
For lot checking, ask for peptide mapping rather than intact mass alone.
edited 23 May 2025 by jana_horakova — corrected a unit error in the worked example
Ask PeptideStack is a static archive. Posting is closed, but the norms are worth stating: answer the question that was asked, show your working, cite the trial or the certificate, and say plainly where the evidence runs out.